1. Field of the Invention
The present invention relates generally to a sealed electrical switch assembly, and more particularly to an electrical switch assembly fixed within an enclosure, and completely encapsulated by a waterproof compound that is resiliently flowable to enable relative movement between certain components of the switch assembly.
2. Description of the Prior Art
The switches that operate remotely located hot tub or spa heaters, pumps and blowers are preferably located next to the spa for convenient use. However, electronic components located in warm, humid environments such as that around a spa are susceptible to moisture penetration and consequent malfunction. Location of potentially malfunctioning switches where they could be operated by persons in the spa would present an unacceptable risk of electrical shock. Air switches have been used to avoid this, but there are certain disadvantages in using them.
The switch components could be encapsulated in a rigid waterproof potting compound to seal them from the humid spa environment. U.S. Pat. No. 4,268,713, issued May 19, 1981 to Donley et al, is typical of devices that encapsulate components in a waterproof compound to protect them from moisture. A flasher is disclosed having a cavity in which electrical components are located. The cavity is filled with a rigid potting compound to completely seal the components from the environment. However, mechanical switch contacts that must move to function could not be protected by such a compound because the compound would prevent such movement.
Various other methods have been advanced in the prior art to provide moisture protection. The majority involve placement of the switch in a waterproof housing, and then sealing any access openings to the outside with rubber boots, O-rings, gaskets and the like. Unfortunately, in many instances this does not provide complete moisture proofing, and in most other instances such sealing measures fail after a relatively short service life.
The system of my U.S. Pat. No. 4,618,797, issued Oct. 21, 1986, overcomes the deficiencies of the prior art by employing a piezoelectric element that can be flexed to generate the desired signal. The element is located in an enclosure filled with a potting material. The material hermetically seals the element, yet is resiliently deformable to allow the element to flex. The system of the patent has operated successfully, but the manufacture, location and placement of the components has presented certain difficulties.
More particularly, the interior of the enclosure structure had to be specially configured to support the element in the potting material, and to provide a flow port below the element for the material to flow away from that area when the element was downwardly deformed or flexed. The system circuit board was located below and separately of the element, and was supported only by the potting material.
This arrangement required individual placement of the element and the circuit board in proper positions within the enclosure before the enclosure was filled with the potting material. Also, only a spacer and a thin plastic overlay separated the element from the environment. Modification of the system appeared necessary because it was theorized that over a long period of time moisture might possibly migrate to the piezoelectric element along the faying surfaces of the overlay, the enclosure, and the spacer, and then adversely affect operation of the element.